Will you or your audience see DLP Rainbows?

DLP projectors (*Costing less than $15,000) flash parts of a colour one after the other to make the illusion of the whole colour (using your eye/brain visual processing) whereas LCD models project all 3 primary colours (RGB) at the same time so the colour projected is the colour you see, they're also vibrant & natural colours. - AIM

Another problem with some DLP projectors is the bearing on the colour wheel becomes noisy and/or fails as it's spinning at a very fast speed.

There must be a noise & vibration problem else Benq and Infoucs wouldn't need to say:

"..We've re-designed our color wheel for maximum absorption of noise and vibrations. We've also added a damper fixed between the MP622/622c's color wheel and bracket for added reduction in noise and vibration." [Link]

" I also have an Infocus X-1 DLP front projector which are famous for colour wheel noise/failure. Also an air bearing design. Luckily mine only produces the noise when not used for an extended period of time and even then for only a few minutes. When it does occur it is unmistakable, sounding very much like a small circular saw. " [Link]

"..Single chip sequential color projectors (DLP) use a rotating color
wheel that spins at a rapid speed and displays colors
sequentially. For some users this results in images displaying
color break- up or “rainbow effect” which can be annoying and
distract from the viewing experience.."

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It was an awesome picture, amazing contrast, but the rainbow effect was so bad I got headaches. |MORE|

Rainbow test

This test can be played on all DLP & LCD displays to check for rainbows.
Note for best results use the stand-alone .exe/zip download.

• In our opinion if you're easily motion sick, have congenital nystagmus or you're sensitive to flashing lights and your budget is under 15K buy a LCD for most applications.
  |Australia only pre-sales support contact us when you're ready to buy.. |
• Our personal experience is people who suffer motion sickness may also be prone to being "DLP sensitive" but this is just our observation only it has no scientific basis.
• Remember it may be a person watching it, not you that has the problem, that's why we (and others) would not recommend installing 1 chip DLP one in a public place.

Color sequential projectors (1xChip DLP) are best avoided in public settings!

Give your eyes a holiday not a workout! 3LCD projectors are the most widely used projectors in the world. |Click here to see Epson's LCD demo|

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Flashing Lights used as a weapon!

According to Lieberman, the device flashes LED lights at several specific frequencies.

Before your brain has time to adjust to one frequency, the Incapacitator flashes another. Add multiple colors and random pulses and the brain just can't keep up.

"Let's not pretend these are anything less
than a weapon," said Michael Soller of the ACLU

"The longer you look at this, the more you don't want to look at it," said Lieberman. "The closer you are to it, the more intense the effect."

The only ways to escape the effects? "Close your eyes, put your hand up, turn your head away, all of which will give the user the advantage they need," said Lieberman.

"..The flashes temporarily blind a person, as any bright
light would, and the light pulses, which quickly change both in color and duration, also cause what Lieberman calls psychophysical effects. These effects, whose effectiveness depends on the person, range from disorientation to vertigo to nausea, and they wear off in a few minutes.

It’s not clear why the changing light pulses cause this effect, even though the effect has been well documented, Lieberman says Helicopter pilots, for example, have been known to crash because they get disoriented by the choppy flashes of sunlight coming through the chopper’s spinning blades.."

The point of this device is to disorient you, so we modified the video when we showed it on air. If you wish to see the unmodified footage of the device in action, you can click here -- but be warned, you may find the experience uncomfortable.

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Blinded by the Light story by Time Magazine

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A segment of animated footage promoting the 2012 Olympics has been removed from the organisers' website after fears it could trigger epileptic seizures.

London 2012 Olympics branding film causes epileptic seizures

One thing to keep in mind when introducing any kind of flashing on the Web is the possibility of it causing seizures in people who have photosensitive epilepsy. It’s one of the basics of Web accessibility, and the fact that flashing or strobing can trigger epileptic seizures is widely known even among people who do not work in the field of accessibility.

I was first made aware of it back in the early nineties, when I used to do a bit of DJing. I loved using the strobes, but after a girl came up to the DJ booth one night to tell me she’d had an epileptic seizure caused by strobing lights I stopped using them. Strobes are cool, but not when you know they may trigger a seizure in someone on the dance floor.

But it seems that knowledge of the connection between strobing or flashing lights and epilepsy attacks is not as widespread as I thought. Recently a movie clip that was published on the official London 2012 Olympic Games website (Warning! Contains colour combinations that are painful to look at. Yes, really.) contained an animation that caused seizures in at least thirty people. And those are just the people who contacted the charity Epilepsy Action about it.

[NOTE it looks like they have removed the offending flashing logo.. It would be a brave epileptic that knowingly purchased a single chip DLP projector after seeing all the available information in our opinion.. -- AIM]

The same film, created to promote the London 2012 brand, was shown on television, where it also triggered seizures. This is a bit more surprising than the film being published on the website, since there are machine-testable regulations for television footage that make sure it does not trigger seizures in people with photosensitive epilepsy. The London 2012 ad was apparently not tested, and consequently did not comply with the Ofcom safety guidelines, as mentioned by BBC News in Epilepsy fears over 2012 footage.

The film has since been re-edited to remove the seizure-triggering segment. Accessibility issues aside, the logo for the London 2012 Olympic Games has been talked about in plenty of forums. I’ll settle for saying that I’ve seen many logos that are better, but Jack Pickard has a bit more to say about it in London Logo No Go. Hint – he is not overly enthusiastic about it ;-). |Source|

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"..*The cheapest three chip projectors costing about $15,000 USD. While that may seem expensive, it may very well be worth it to minimize screen door and eliminate rainbow effects.." |link|

The DLP "Rainbow Effect"

This visual artifact is best described as brief flashes of perceived red, blue, and green "shadows" observed most often when the projected content features bright/white objects on a mostly dark/black background (the scrolling end credits of many movies are a common example). Some people perceive these rainbow artifacts all of the time, while others say they only see them when they let their eyes pan across the image. Yet others do not notice the artifact at all. The effect is likely rooted in the concept of the flicker fusion threshold .

The "Rainbow Effect" is unique to single-chip DLP projectors. As described above, only one color is actually displayed at any given moment. As the eye moves across the projected image, these separate colors become visible, resulting in a perceived "rainbow". The manufacturers of single-chip DLP projection systems have used color wheels rotating at higher speeds, or with more color segments, in order to minimize the appearance of the artifacts. These are referred to as 2x, 3x or 4x wheels. For example, a six segment wheel(RGBRGB) rotating at two revolutions per frame would be a 4x wheel.

Another way to reduce the rainbow effect is to replace a segmented wheel with a wheel whose colors are in an Archimedean spiral . This forms bands of color that move down (or up) the screen. With segmented wheels, the DMD must "go black" while the wheel transitions from one color to another. Not only can this interfere with persistence of vision and thus accentuate the rainbow effect, it means that the more segments there are, the darker the display will be, all else being equal. With a spiral wheel, the mirrors can display more than one color at a time, each moving down (or up) as the wheel turns.

The LED light packs now being introduced in DLP projectors may eliminate rainbow effect for all but a few very sensitive viewers thanks to their high switching frequency and a complete lack of "black" segments as described above. Additionally, the LED pack can display any color of light at any intensity, a capability which, if exploited, provides the potential for increased color gamut and improved contrast compared to displays employing color wheels with fixed-color segments.

Source http://en.wikipedia.org/wiki/DLP who no doubt will have legal action coming too :)

A Potential Problem with DLP: The Rainbow Effect

If there is one single issue that people point to as a weakness in DLP, it is that the use of a spinning color wheel to modulate the image has the potential to produce a unique visible artifact on the screen that folks refer to as the "rainbow effect," which is simply colors separating out in distinct red, green, and blue. Basically, at any given instant in time, the image on the screen is either red, or green, or blue, and the technology relies upon your eyes not being able to detect the rapid changes from one to the other. Unfortunately some people can. Not only can some folks see the colors break out, but the rapid sequencing of color is thought to be the culprit in reported cases of eye strain and headaches. Since LCD projectors always deliver a constant red, green, and blue image simultaneously, viewers of LCD projectors do not report these problems.

How big of a deal is this? Well, it is different for different people. For some who can see the rainbow effect, it is so distracting that it renders the picture literally unmatchable. Others report being able to see the rainbow artifacts on occasion, but find that they are not particularly annoying and do not inhibit the enjoyment of the viewing experience. Fortunately, the majority of the population either cannot detect the rainbow artifacts, or if they can they are not overly bothered by them. The fact is if everyone could see rainbows on DLP projectors the technology never would have survived to begin with, much less been embraced by so many as a great technology for home theater video systems. Nevertheless, it can be a serious problem for some viewers.

Source http://www.projectorcentral.com/lcd_dlp.htm

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DLP vs. LCD - Which is Better?

The potential drawback of this single-chip DLP technology is that in any given instant, the picture on the screen is not the total image, but is instead rapidly alternating between images consisting of the individual red, green, and blue colors. Thus the eye and the brain play the last critical role in making single chip DLP projectors work, by combining or averaging or integrating the picture, so that the viewer perceives the desired image and not the rapidly flashing momentary components of the image.

With a static picture from a single-chip DLP-based projector, it is easy to understand how this averaging works just fine. Where things potentially start to fail is when there is motion in the image, or when one blinks or rapidly moves one's eyes quickly between various parts of the image. In these cases, the perceptual integration of the image may break down and one might see "rainbows" or false flashes of color, in the image. Some individuals have also reported getting headaches after watching single-chip DLP projectors for any length of time. It appears that not all individuals handle this color averaging process equally well. Newer single-chip DLP-based projectors use a higher speed (5x) six segment color wheel, thus greatly reducing the likelihood that an individual will perceive these artifacts. Also, Double Data Rate (DDR) DMD chips reduce artifacts even further by updating the information going to each mirror at a faster rate.

Source http://www.hometheaterhifi.com/volume_10_3/feature-article-dlp-vs-lcd-which-is-better-7-2003.html

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Your HDTV: Projecting a Good Image

Most people don't notice a situation with DLPs called the rainbow effect. This is caused by the spinning color wheel, and can cause a very small percentage of the population to feel dizzy, or get a headache, while watching DLP - particularly when moving their heads, or during rapidly moving scenes on-screen.

Source http://www.dummies.com/WileyCDA/Section/id-129194.html

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Forums

My personal experience is that I was also highly susceptible to them when I first viewed the X1 DLP projector. Indeed, after my first hour of viewing I felt a nauseous headache coming on (I also get car sick by the way - so perhaps this is an indication?).

Source http://www.audioenz.co.nz/forums/archive/index.php/t-561.html

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Visual Fatigue

Visual Fatigue in Congenital Nystagmus Caused by Viewing Images of Color Sequential Projectors (DLP 1x Chip) - Journal of Display Technology- Vol.1- No.2 - pp.314 - 320

Masaki Ogata, Kazuhiko Ukai and Takashi Kawai

Color breakup is the perceived splitting of the white portions of an image into its red, green, and blue components when the image is projected with the color sequential method and the viewer is moving his or her eyes. This study aims to evaluate how color breakup affects symptoms of visual fatigue in people with congenital nystagmus. The eyes of people with congenital nystagmus continuously oscillate leading to color breakup without pause. One in every 1 500 persons is afflicted with congenital nystagmus.

Many sufferers have almost no symptoms in daily life except for a mild deterioration of visual acuity. Five subjects with congenital nystagmus were shown a 15-min portion of a movie projected with three video projectors (one liquid cyrstal display (LCD) projector and two single-chip digital light processing (DLP) projectors). They were subjectively evaluated both pre- and post-viewing with a questionnaire listing visual fatigue symptoms. One subject was tested in an additional experiment using six more projectors.

Results indicated that subjects with congenital nystagmus felt severe visual fatigue after they viewed images produced by color sequential projectors. Mechanism of the cause of visual fatigue is not clear in general and in color breakup in congenital nystagmus, however, it was clear that people with nystagmus felt continuing color breakup as a flickering image. Flickering light is a major cause of visual fatigue.

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Color sequential projectors are best avoided in public settings, such as classrooms, lecture theaters and conference sites."

Source http://www.audioenz.co.nz/forums/archive/index.php/t-561.html

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The 3LCD

Group is also producing collateral materials and advertisements for consumers and industry professionals that further rein- force many of the core benefits of 3LCD prod- ucts as shown at CES. These include: a.. "No Color Breakup" - since this technology simultaneously projects three full-time red, green and blu e images, there is no color breakup or " rainbow effect" to potentially cause viewers eyestrain or visual fatigue.

Source JULY 2005 / WWW.PCWORLD.COM

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Source http://www.audioholics.com/techtips/specsformats/displays_DLP_technology2.html

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Rear-projection TVs: CRT , DLP , LCD , and LCoS

One potential problem with DLP sets is known as the rainbow effect. Some people can see brief streaks of color on these TVs, especially when moving their eyes across the screen. This is caused by the fact that the single DLP chip uses a color wheel to create red, green, and blue, and hence all colors. The occurrence of these rainbows has been significantly reduced with the advent of newer, faster color wheels, and most people who watch a DLP never see rainbows at all (and the few who do usually see them only occasionally). DLP HDTVs do introduce a bit more low-level video noise, which can look like tiny dancing pixels or motes in shadowy areas, than other microdisplay TVs.

Source http://reviews.cnet.com/4520-6463_7-5023901-4.html

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High resolution image of a DLP "Rainbow"

http://upload.wikimedia.org/wikipedia/commons/c/ca/DLP_rainbow_effect.JPG

Photo taken of a hand moving quickly past a DLP projection, demonstrating the rainbow effect of a DLP projector's colour wheel. (This is an Acer PD100) Author: Damien Donnelly

And finally (for now)

DLP TV Minus

DLP is very comparable to LCD's rear-projector models. The two display types compete for attention at the local retailers and LCD has gained converts from serious players in the video market. Samsung sees DLP as the future of rear-projection displays and has invested a lot of research and development into fine tuning their line of DLP TVs. The results are some of the finest big-screen HDTVs on the market.

DLP doesn't suffer the screen-door effect of LCD projectors because the pixels are literally closer together with a DLP TV. However, DLP is not without its own technical drawbacks. Notably is the rainbow effect, which only a certain segment of the population can even see at all. Those who can see the "rainbow" in a DLP TV claim to get headaches from extended viewing. Most don't see it at all and this is probably thanks to a lot of proprietary processes developed by the likes of Samsung to use lenses that filter out any of the adverse effects. Although DLP is a much newer display technology than LCD, it's made strides since its development and is here to stay for the foreseeable future.

Source http://www.gizmocafe.com/tv-video/dlp-tvs.aspx

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**The Ultimate Rainbow Discussion Thread**

"..Why are you DLP guys who aren't bothered by them so insensitive to other people? What if your best friend turns out to be someone who gets a migraine headache any time he sees flashing lights? You're gonna put your strobe light out for the party every time he comes over because you're not going to worry about the minority?.."

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PS

A new staff member at AIM that hadn't had a migraine in five years had such a bad one in his first week (after a DLP projector demo) that he had to be driven home. After the second incident a week later he was banned from all DLP demonstrations. He had no ill-effect whatsoever when watching LCD models. So we have first hand knowledge of how some people are not well suited to watching some single chip DLP models. -- AIM

(Alternative to DLP) Five of the world’s leading and most-recognized consumer and business electronics manufacturers – Fujitsu, Hitachi, Panasonic, Sanyo and Sony – have joined forces with Epson, the country’s leader in digital imaging solutions, to educate consumers and video display professionals about the significant benefits of three-panel liquid crystal display (3LCD) technology. The 3LCD Group was unveiled at the recent International Consumer Electronics Show (CES) 2005 held in Las Vegas. "3LCD is clearly the dominant microdisplay technology worldwide when you look at the total number of customers who have purchased front an rear projection products so far,’’ according to Dr. William Coggshall, Pacific Media Associates. "Based on our calculations, over nine million projection products using 3LCD technology have been purchased to date, surpassing any other microdisplay technology on the market, and that figure continues to grow at a rapid pace.    October 2005 - APC Labs comparisons:- In relation to DLP models:- "Since the rainbow effect can cause eyestrain and headaches, ask for a demonstration of the unit (45 min) you're thinking of buying. Flick your eyes around as you watch and check for artifacts or colour blurring.."